What is the difference between Tibetan Buddhism and the Theravada and Mahayana schools?

Tibetan buddhism is more similar to Theravada buddhism in that the believe in Lord Gautama as Buddha not as God as the Mahayanists(chinese) belief and the belief in multiple Buddhas that are reborn to stay and help people with their salvation.But that contradicts the Buddhas edicts and hence is not generally accepted as fact but more of a chinese sect.Buddha said"Be a lamp unto yourself and not seek external refuge"